1. Technical Field
The present invention relates to a motor control circuit and a power window device provided therewith.
2. Related Art
Conventionally, there are well known various power window devices including a window, a motor that opens and closes the window, and a motor control circuit that controls the motor (for example, see Japanese Unexamined Patent Publication Nos. 2007-224637 and 2008-106560). In such power window devices, a window opening operation is performed by a normal rotation of the motor, and a window closing operation is performed by a reverse rotation of the motor.
In the power window device disclosed in Japanese Unexamined Patent Publication No. 2007-224637, a manipulation knob is provided so as to be switched to positions of “automatic closing AC”, “manual closing MC”, “neutral N”, “manual opening MO”, and “automatic opening AO”. In the power window device, once the manipulation knob is switched to the position of “automatic closing AC”, the window closing operation is continuously performed even if the manipulation knob is returned to the position of “neutral N”. The power window device stops the window closing operation when detecting that a foreign substance is caught in the window during the window closing operation. The detection that foreign substance is caught in the window is determined based on a rotating speed of the motor.
In the power window device disclosed in Japanese Unexamined Patent Publication No. 2008-106560, the window opening and closing operations can be performed even if a vehicle is submerged. Therefore, the window opening operation can be performed even if the vehicle equipped with the power window device is submerged in a sea or a river, so that a driver can be prevented from being locked in the vehicle.
A catch preventing function and a function of performing the window opening operation in the submerged state, as described above are demanded for the power window device. There has been proposed a power window device having the functions (for example, see WO 00/37761).
The power window device disclosed in WO 00/37761 includes a first relay circuit that normally rotates the motor and a second relay circuit that reversely rotates the motor. The first relay circuit includes a first coil through which a current is passed when a manipulation switch is turned on to open the window and a first relay contact that connects the motor to a power supply when the current is passed through the first coil. The second relay circuit includes a second coil through which a current is passed when a manipulation switch is turned on to close the window and a second relay contact that connects the motor to the power supply when the current is passed through the second coil.
In the power window device disclosed in WO 00/37761, a switch element is provided to short-circuit both ends of the second coil when the manipulation switch is turned on to open the window. The switch element is interlocked with the manipulation switch that is used to open the window. The power window device is submerged, and the manipulation switch used to close the window is short-circuited to pass the current through the second coil. Even in such cases, when the manipulation switch used to open the window is turned on, the switch element short-circuits both the ends of the second coil, so that the current can be passed only through the first coil. Accordingly, in the power window device disclosed in WO 00/37761, the window opening operation can be performed in the submerged state.